They’re not fat, they’re just big-brained: Tiny spiders have such huge brains for their body sizes that the organs can spill into the animals’ body cavities, a new study shows.
Such big brains may explain why very small spiders—some less than a millimeter across—are just as good at spinning webs as bigger arachnids.
For the study, a team led by Bill Eberhard, a staff scientist at the Smithsonian Tropical Research Institute and a professor at the University of Costa Rica, examined nine spider species from six web-weaving families.
The researchers found that the smaller the spider, the bigger its brain relative to its body size.
In some spiders, the central nervous system took up nearly 80 percent of the space in their bodies, sometimes even spilling into their legs.